A 12-week vegan diet can lead to meaningful weight loss and modest improvements in blood sugar control in overweight adults and people with type 2 diabetes, according to a new meta-analysis of 11 randomized controlled trials.
The findings, based on data from nearly 800 participants, were presented at the European Congress on Obesity (ECO) in Maastricht, the Netherlands.
The research was led by Anne-Ditte Termannsen from the Steno Diabetes Center Copenhagen in Denmark.
The analysis found that while vegan diets were associated with significant reductions in body weight and body mass index (BMI), they had no clear effect on blood pressure or triglyceride levels.
Researchers conducted a systematic review and meta-analysis of all relevant English-language randomized trials published up to March 2022.
The studies compared vegan diets with other dietary approaches in terms of cardiometabolic risk factors, including body weight, BMI, blood sugar levels, blood pressure, cholesterol levels, and triglycerides.
Vegan diets were evaluated against either passive control groups, in which participants continued their usual diet, or active control groups, which followed alternative dietary interventions.
In total, data from 11 studies involving 796 individuals were included. Participants were between 48 and 61 years old on average and had either overweight or type 2 diabetes. All trials lasted at least 12 weeks, and a weight loss of 5 kilograms or more was considered clinically meaningful.
Compared with control diets, vegan diets led to a significant reduction in body weight, with an average loss of 4.1 kilograms, as well as a decrease in BMI of 1.38 kg/m².
However, the effects on other outcomes were relatively small, including reductions in blood sugar levels (−0.18 percentage points), total cholesterol (−0.30 mmol/L), and low-density lipoprotein (LDL) cholesterol (−0.24 mmol/L).
The researchers observed that weight loss and BMI reductions were greater when vegan diets were compared with no dietary changes, rather than with other structured dietary interventions.
Termannsen noted that the findings provide reasonable certainty that following a vegan diet for at least 12 weeks can support weight loss and modest improvements in blood sugar control. As such, vegan diets may represent a viable management strategy for individuals with overweight or type 2 diabetes.
The authors suggest that weight loss associated with vegan diets is likely driven by reduced calorie intake, due to lower fat content and higher dietary fiber intake. However, they emphasize that more evidence is needed to clarify the effects of vegan diets on other cardiometabolic outcomes.
Several limitations were noted, including the relatively small sample sizes of most trials and substantial variation in vegan diet composition, particularly with respect to carbohydrate, protein, and fat intake.
The researchers caution that observed health effects may be partly explained by differences in macronutrient composition and total energy intake between the intervention and control groups.
